In the copending, commonly assigned application Ser. No. 540,531 entitled "Scanning Optical Spectral Analyzer Employing Plural Detectors" of Dapper et al., there is disclosed a device wherein a field of view is scanned to determine spectral information of a point source of optical radiation. First and second displaced optical detector means for imaged radiation from a point source being monitored are respectively provided in first and second optical paths that are substantially simultaneously established with a scanner having an instantaneous narrow field of view. In the second optical path, a narrow bandpass filter is provided to establish a reference time position for a predetermined wavelength of the source. In the first optical path, a dispersion means, such as a prism, is provided so that different wavelengths of the source are convoluted onto the first detector means at different times during a scan of the field of view. The convoluted wavelengths cause the first detector means to derive a time varying analog signal having a predetermined waveform including an initial peak value followed by a predetermined time varying undulation. The undulation is indicative of the spectral properties of the imaged point source and enables different sources to be distinguished from each other.
A problem in recognizing the undulations of different point sources is that the occurrence time of the first peak is unpredictable, as the source has a random position anywhere in the field of view. Also, the amplitude of the undulations has a tendency to vary depending upon the distance between the point source and the detector, even though the shape of the waveform remains relatively constant for a particular point source.
It is, therefore, an object of the present invention to provide a new and improved apparatus for distinguishing different time varying analog signal sources and enabling signal sources having predetermined waveform characteristics to be determined.
Another object of the present invention is to provide a new and improved apparatus for enabling a particular source of optical radiation in a field of view being scanned by an optical scanner to be distinguished from other sources of optical radiation.
A further object of the invention is to provide a correlator for distinguishing different point source optical images resulting from a convolution of dispersed optical energy from the source.
An additional object of the invention is to provide an apparatus for enabling a particular source of optical radiation in a field of view being scanned by an optical scanner to be distinguished from other sources of optical radiation even though the position of the source is random.
A further object of the invention is to provide a new and improved waveform recognition system wherein wave shape variations are matched, even though there is an appreciable variation in the amplitude of a signal comprising the variations.